nicolson



March 1, 1932. v A. M L. NICOLSON 18,372

SCANNING SYSTEM FOR TELEVISION Original Filed Oct. 26. 1927 2 Sheets-Sheet 1 5 V i/Z5 INVENTOR Alexander M lean M'cb/son.

, WKW

ATTORNEY March 1, 1932. A. M L. N|CQL$ON Re. 18,372

SCA NNING SYSTEM FOR TELEVISION Original Filed Oct. 26, 1927 2 Sheets-Sheet 2 Y 69 IE :1. :s- E A 67 g 54 :1 52 F L {i 8! 2 l l I c? 2' Q 5041 H 'I ll II l 4 55 INVENTOR 4/exander '/7 Lmn N/co/sorl ATTORNEY Reissued Mar. 1, 1932 UNITED STATES PATENT OFFICE ALEXANDER MCLEAN NICOLSOltT, OF NEW YORK, N. Y., ASSIGNOB; T0 COMMUNICATION PATENTS, INC, OF NEW YORK, N. Y.

SCANNING SYSTEM FOR TELEVISION Original No. 1,779,749; dated October 28, 1930, Serial No. 228,712, filed October 26, 1927. Renewed March 21, 1930. Application for reissue filed This invention relates to a method of and;

apparatus for transmitting and reproducing images electrically and more particularly to a method of and apparatus for such transmission and reproduction at speeds sutiicient to create the illusion of motion, commonly re this process may take place rather slowly, but

in case it is desired to transmit images of moving ob ects, the process must be speeded up to such an extent that approximately SlX- teen complete images are sent and reproduced per second, this number being suificient to present the illusion of motion.

It has been usual in the past in the transmitter to utilize a photo electric cell supplying in its output circuit a current or voltage proportional to the intensity of light falling thereon, and to provide apparatus, which operates to cause the light from the successive unit areas of the object to fall successively upon the photo electric cell. This apparatus is termed the scanning apparatus-and is utilized not only for the purpose just described in the transmitter, but similar apparatus is utilized in the receiver for the purpose of' causing the source of light at thereceiver to follow the movement of the scan-- ning apparatus at the transmitter and to reconstruct the image to be reproduced.

In my copending application entitled Method and apparatus for television and the like, Serial No. 218,425, filed Sept. 9th, 192?, I have described an arrangement in which the area to be scanned is illuminated by an electrical are or discharge which passes over the entire area to be scanned in a predetermined path or pattern. In the arrangement the-re described, the arc or discharge position In the case-- December 19, 193 Serial No, 503,577.

is fixed or determined by relative moveQ ment of theelectrodes between which the discharge takes place, and at least one of the electrodes of the system is a point, with respect to which the discharge does not move,

By reason of this construction, the s-peedof travel of the discharge is limited to the in which the scanning discharge in playing over the area travels at a velocity'greatly 1n excess of the velocity of movement of the electrode system.

It is-a further'object of this invention to provide a scanning system in which the positionof the discharge is always fixed by the space relation between the electrodes from which the discharge takes place, but in which, nevertheless, the discharge passes over the screen at a velocity greatly in excess of the actual velocity ofthe moving electrodes.

It is still a further object of this invention to provide a scanning system utilizing a pair of continuously relatively movable electrodes for causing a discharge to pass repeatedly in a predetermined patternover the area to be scanned, at a rate of speed relatively much higher than the rate of movement of said electrodes. Still other objects and advantages of my inventionwill be apparent from the specification.

The features of novelty which I believe to be characteristic of my invention are set forth with particularity inthe appended claims. My invention itself, however, both as to its fundamental principles and as to its particular embodiments, will best be un derstood by reference to the specification and accompanying drawings, in which:

Figures 1, 2 and 3 are diagrammatieviews of similar forms of apparatus according to my invention, but differing slightly in detail. V

. Figures 4 and 5 are respectively, side and of which preferably approach each other at a small angle andpass over and by each other front elevations of one formflof' apparatus according to my invention.

Figure 6 is a diagrammatic view of still another form of apparatus according to my invention. I V

Figure 7 is a diagrammatic View of still a further form of apparatus according to my invention; and,

' F igure8 is aside View of apparatus in accordance therewith.

In. accordance with my invention, I provide a method and apparatus whereby a luminous, electrical discharge is produced and caused to follow ata high rate of speed a predetermined scanning pattern intravelling over the area to be scanned, until all individual unit areas have been illuminated by the saiddischarge. The discharge itself, may be direct current or alternating current of any desired frequency, or any combination of the same, but preferably a relatively highfrequency is utilized. The discharge may be made to take place in the Open air or in an enclosed chamber containing air under any desired pressure, greater or less than atmospheric, or other gases or mixture of gases may be utilized either with or with: out finely I divided solid or liquid: gases, such as neon, at a relatively low. pressure, such as a few millimeters of mercury, are satisfactory.

The electrode system. between which the discharge takesplace, comprises a pair'of relatively movablepelectrodes so formed and moved with respect to each other, that the discharge passing between them travels at a rate of speed much greater than'thespeed of the electrodes. The form of the electrodes may be varied within the spirit of my invention, 'butin general it may be said that the electrode systems are characterized by a pair relatively movable linear members,

Without actually making contact, whercby the straight line representing the shortest distance between the two electrodes'atany given instant, and impinging on the electrodes at points whichI' term intercepts, is, caused to pass very rapidly alongthe surface of the electrodes. A difference of potential is maintained between said electrodes, whereby as the electrodes pass by each other, a discharge passes across the path representing the shortest distance between the said electrodes, which discharge passes laterally rate of speed.

Referring now more particularly to along theelectrodes at a high Fig- . ure 1, 1 designates one of a pair of relative ly' movable frames upon which the electrodes are mounted. In this instance, 1 may be a rod or'bar of any suitable material, either conducting or insulating, and having mounted thereupon a series of are or discharge points, such as 3, 4,5, 6, 7, 8, 9, 10 and 11 projecting outwardly therefrom, all of which points are connected to ether and to one terminal of the source 0 potential which causes the discharge. The other electrode system is designated generically by the numeral 2 and comprises a plurality of spaced electrodes 15, 16, 17, 18, 19, 20, 21 and 22,

maintained in fixed relationship with eachother, in any suitable manner as, for en ample, being mounted upon the frame members'23 and 24'. 'All of thesaid electrodes ,of. the-electrode system 2 are connected to-.

gether into the opposite terminal of the source of potential; It will be understood.

that the number and spacing shown is purely diagrammatic andintended only to illustrate the principle of the invention, it

being necessary to provide a suflicient number of individual electrodes and sufficiently closelyj spaced to supply the requisite detail for any particular image which it is desired to transmit. ltwill further be under-v stood that in the case of a small image in which there is a large amount of detail, the electrodes will naturally be spaced closel together and a greater number will be utilized than in the case when the image is largerand comprises less detail.

The source. of potential may comprise a source of alternating current, such as 26, of any desired frequency. The source 26 may be any convenient instrumentality for, supplying the frequency desired. If the frequency desired is relatively low, an alternator may be utilized, while if a high frequency is de I sired, the source 26 will preferably be a vacuum tube oscillator, or the equivalent. While I, have shown a single source 26, it will be understood that a plurality may be provided.

of diiferent frequencies, if desired: in addition, a source. of direct current, such as battery 25-or a direct current generator, may be utilized. The sources 25 and 26 may be shunted by a circuit containing inductance If now, the electrode systems 1 and 2 be arranged so as to be relatively movable in a manner to pass through overlapping relation without actually making contact, anda sufficient difi'erence of potential be maintained between the electrode systems, then as the member 1 passes by the electrode system 2,

a spark or discharge will pass between the intercept points of the two systems; that is to say, assuming the electrode member 1 to have a movement in the direction shown by the arrow A and assuming the electrode system 2 to be stationary, then it will be seen.

that the discharge points, 3, 4, 5, 6, 7, 8,, 9', 19 and 11 will successively pass by'the electrode 1.5, and it the electrode systems be main tained in parallel relation and the magnitude of potential difierence between them be properly controlled, at the instant that each of be seen that if the angle between the line of electrodes, 3, 4-, 5,. 6, 7, 8, 9, 10 and 11 be designated as the distance between the two end electrodes 3 and 11 be designated as c, and if a line be drawnirom the electrode 3 parallel to theelectrode 15, and if a projection perpendicular thereto be dropped there on from the electrode- 11 and this projection be designated as a. and the projection. of the line- 0 upon the line parallel to electrodc15, be designated as b, itwillbe noted that there is formed a triangle, one of whose angle. is a right angle, and we may establish the equation:

I I tan 0: from which it follows that a ubn tan r made very small, cot or becomes increasingly large: or in other words, the smaller the angle between the electrode systems 1 and 2, the greater the discharge velocity in the direction 'B, or conversely, the smaller the necessary velocity of. the electrode system in the direction A, in order to obtain any desired discharge velocity in the direction B.

It will bennderstood that while mathematically an infinite velocity of discharge in the. direction B is obtainable with a very small angle or nevertheless, there are practical limits imposed beyond which it becomes difficult to go that is, if the angle o: is made extremely small, the diile-rence in distance between the electrode 3 and the electrode 15, and electrode 11 and electrode 15, may become so small that ionization. of the space between the electrodes or slight impcriections in the surface of the electrodes or other causes, may prevent. the. discharge. from taki'ng place at the proper time, and thereby interfere with the operation of the system.

In general, however, it will be understood that it will be desirable to operate with as small; an angle of incidence as may be obtained without interposing excessive difiiculties in the control of the discharge.

lVhile I have explained the principle of my invention with respect to the electrode 15, it will be understood that this electrode scans only a single line of the picture, and that the additional electrodes 16, 17 etc., are provided for scanning the additional lines of the picture, and that, as the electrode 1 passes acrossthe additional electrodes, a discharge passes in the manner already described. The angle 0: will preferably be made suiiiciently small with respect to the spacing between the eleo-;-

trodes 15, 16, etc., that the discharge between the electrode 11 and the electrode 15 terminates before the discharge begins between the elect-rode 3 and the electrode 16, as, if this] were not the case, it would be necessary to insulate the various electrodes and to provide commutating devices for -multiple channel operation, which is, for certain purposes, undesirable as it complicates the apparatus and operation, although it will be understood that my invention may be applied for multiple channel operation in the manner described in my patent entitled Method andapparatus for television and the like, No. 1,77 9,7 47, issued Oct. 28, 1930. I

The electrode system 1 may comprisejpoints or projections of anysuitable material such as platinum, cadmium or other conductor,-suitably chosen with respect to the nature of the light radiation desired, and also with respect to its life in operation, and the electrodes 15, 16, 17, etc., may consist of wires, or filaments, provided if desired with discharge points or serrations, or these electrodes may consist of knife edges, either plain or provided with projections, to locate the discharge. The entire electrode system, comprising both movable and stationary electrodes, may operate .in open air or within a container comprising air under pressure either greater or less than atmospheric, or suitable gases or mixtures of gases may be supplied to the container, either with or without the exhaustion of air: for example, the discharge may take place within the container comprising neon under a pressure of a few millimeters, or mixture of neon and helium, or the like: in addition, finclydivided solid material. or substance capable of vaporization may be utilized, such as mercury. metallic salts and thelike, it being understood that the optimum conditions of operation may differ with the nature of the current utilized. An opaque screen, provided with a lens, may be interposed between the electrode system and the image or the screen, for the purpose of focusing, in the manner shown and described in my copending ap- I In the receiving arrangement, the operaplications, entitled Method and apparatus for television and the like, Serial Number 218,425, filed: Sept. 9th, 1927 High speedtelevision system, Serial .N'o. 222,417,"filedi Sept. 28, 1927; and Pilot television system, Serial Number 225,415, filed October 11, 192-7..

I The discharge is preferablyso controlled in the transmitter as to have a constant luminous intensity, and isarranged to play over". a; successlve areas of the sub ect; 1n addition,

suitable fixed lights may be utilized to fur nish a steadyillumination of the subject, and one or more photoelectric cells are provided, adapted to receive light from the subject, in

1. the manner described in my copendin'g appli' cations above referred to, the output of which may be utilized to control any suitable transmitterqAs my invention in this instance is not limited to any particular form of trans;

" mitter or receiver, I do not'b elieve it necessarytodescribe the same'in detail, reference being had to the above identified applications for details of systems with which my inven tionmay bentilized.

,7 tion of the scanning apparatus is substantially the'same as in the transmitter apparatus except that the luminous intensity of the discharge is controlled in' ac'cordance' with the output of the photo electric cell or cells at the transmitter by supplying avoltage to'the electrodes which corresponds to the photo electric cell output, or by controlling the impedance ofa path supplied with constant voltage in accordance with the photo electric cell output, or both, or many other suitable manner as mo're particularly de-- scribed in the above identified applications, to which reference is had. p It will also be understood that the invention is notlimited to operation with visible light, but that obscure or invisible light may be utilized, such for example as the infra-red or ultra-violet endof the spectrum.

Referringnow more particularly to Figure 21 have shown the electrode 1 as being provided' with a single electrode 12 instead of-the plurality of electrodes as in Figure 1, the

other parts being unchanged. In this instance, it will be understood that if the electrodes 12 and 15 are knife edges, the discharge produced will be continuous rather than in termittent as is the casein Figure 1. I

Referring nowmore particularly to Figure 3, Ihave shown an arrangement in which the electrode 1 is disposed perpendicularly to the frames 23 and 24 for movement in the same direction as in Figures 1 and 2, whereas the electrodes of system 2 are disposed at an angle other than a right angle to the frames 23 and 24. In this instance, the electrodes of the system 2 may comprise Wires, ribbons or knife edges 30, 31, 32, 33, 34, 35, 36, etc., arranged in a zigzag manner, and it will be noted that as the electrode 13 passes downward in the direction shown by the arrow C; the dis 1 charge passes back and-forth acrossv :the screen, Ireversingits direction at each edge as shown by the arrow B, whereas in- Figures 1 and2,the discharge passes across'the screen always in the same direction.

Various arrangements may be producing the relative motion. of the sort required between the electrode systems, one of which is shown diagrammatically in Figures 4 and 5, wherein the bars 1 are mounted upon a pair of travelling chains and 51. A pair of sprocket wheels 52' and 53 mounted on the shaft 54; are provided for carrying the upper loops of the chains, and'a similar pair utilized for of sprocketwheels 55 and 56 are provided at the lower loops of the chains, which sprocket wheels are mounted on suitable shaft 57; 'For' the purpose of preventing any slack inthe chains from disturbing the inner-electrode space and thereby affecting the discharge,

suitable guides and 8 1"may be provided. within which the straight portions of thechains are adapted to run,1 -whic h guides pre-' vent anywobbling in the chains, an'dfcorre spending (disturbances of 'theposition of the electrodes. The shaft 57 may be rotated by any suitable'prime mover such' as syn chronous motor 82. Still other arrangements may be used, such for example as-electrodes reciprocating. in guides at as'nearly uniform velocity as possible.

An opaque screen S provided with a lens L may be-provided to focus thedischarges upon the object 0 whose image is to be transmitted, and in this instance photo-electric cells 84 and 85 may be provided to receive light reflected from the object;

Referring now more particularly to Figure 6, I have-shown a still further modification" of the electrode system in this instance, there may beprovided a multiplicity of radialelectrodes such as 62, 63, 64, 65, 66, 67, 68 and '69. A rotating lever or carrier rod 61 is provided, pivoted-at a point slightly eccentric with respe'ct to the radial electrodes and on this carrier rod there may be provided anele'c trode .60 which maybe a wire or filament,

ribbon or knife edge, as already described.

V This electrode'60 will preferably extend from the center to one end'of the carrier rod 61.

Upon rotation of the carrier rod 6l, it will be observed that the electrode 60 passes each of the radial electrodes at a slight angle in the direction indicated by the-arrow A, and the discharge travels along the radial electrodes in a direction indicated by the arrow B. i

Referring now more particularly to Figure 7 "I have shown an arrangement in which the area to be scanned is covered by a discharge travelling in a spiral pathrather than in a rectilinear path, as is the case withf'the arrangements already described. In this instance, 70 and'7l represent spiral electrodes which.may, for example, be in a form similar to the well known clock spring. If the spirals be made of .difierent pitch, the relative rotation of the two electrodes and 71 will cause the discharge to move inwardly from the outer end of the electrodes to the inner end, and if the spirals be so chosen that the outer and inner ends of each spiral coincide, T then for one complete rotation of either spiral with respect to. the other, the discharge will pass from one extremity of the spiral to the other. The spirals may. also be made identical and arranged slightly eccentric to each other by an amount preferablyless than the pitch. Referring now more particularly to Figure 8, Ihave shown a side view of an arrangement illustrating the application of the principle of Figure 7. In this instance, 70 and 71 are side views of the spiral electrodes, the electrode 7 0 being mounted upon a backing plate 72, which, in this instance, may boot-transparent material such asglass or quartz: electrode 71 is mountedupon a suitable backing plate 73, which in turn is mounted upon shaft 74 of a suitable motor or other rime mover 75, which may rotate the electrode 71 with respect to the electrode 70.

While I have shown and described certain preferred embodiments of my, invention, it will be understood that changes and modifications may be made without departing from the spirit and scope of my invention, as will be understood by those skilled in the art.

I claim 1. The method of scanning for television and the like which comprises maintaining between a pair of relatively movable linear electrodes a difference of potential suflicient to cause a discharge to pass between intercepts, and moving said electrodes relatively in such manner as to cause said discharge to travel along said electrodes with a velocity in excess of the velocity of movement of said electrodes to cause successive illumination of unit sections of the area to be scanned.

2. The method of scanning for television cause successive illumination of unit sections of the aiea to be scanned. I

3. The method of scanning for television and the like, which comprises maintainingv between a pair of relatively movable linear electrodes a difference of potential suliicient to cause a discharge to pass between intercepts, and varying the relative position of said electrodes to cause said discharge to electrodes a difi'erence ofpotential sufiicient to causea discharge to pass between intermove and with a. velocity in. excess of the velocity-of movement of said electrodes, and in a direction other than. the direction of such movement to cause successive illumination of unit sections of the area to be scanned. 4. 'ihe methodof scanning for television and the like, which comprises maintaining between a pair of relatively movable linear cepts, and moving said electrodes relatively to-each other in a direction different from that or the direction of movement of said discharge desired, to cause said discharge to travel witha velocity in excess of the velocity of movement of said electrodes to cause successive illumination of unit-sections of the area tobe scanned. I 5. The method of scanning for, television and the like, which comprises maintainingv between a pair or" relatively movable linear electrodes a ditl'erence of potential sui'ficient to cause a discharge to pass between intercepts, and continuously moving said elec trodes, relatively in the same direction at an angleto the direction of travel of discharge desired, to cause said discharge to travel along said electrodes at a velocity in excess of the velocity of movementof said electrodes to cause successive illumination of unit sections of the areato be scanned.

6. The method of scanning fortelevisi-on I and the like, which comprises maintaining between a pair of relatively movable linear electrodes, a diflerence of potential sufficient to cause a discharge to pass between intercepts, maintaining an angle less than 459 between said electrodes, and moving said electrodes relatively in a direction normal tothe line of one of said electrodes,- to cause said discharge to pass along-said electrodes with a velocity exceeding that of said electrodes to cause successive illumination of unit sections of the area to be scanned.

7. Scanning apparatus for television and the like, comprising a pair of relatively movable linear electrode systems, arranged at an angle with each other, means for maintaining between said electrodes a potential sufficient to cause adischarge between intercepts, and means for moving said electrodes relatively in a. direction normal to the line of one of said electrodes while maintaining the angular relation between said electrodes to cause successive illumination of unit sections of the area to be scanned.

8. Scanning apparatus for television and the like, comprising a pair of relatively movable linear electrode systems, means for maintaining between said electrodes a potential sufficient to cause a discharge and means for moving said electrodes relatively in such a manner as to cause said discharge to travel along said electrodes'with a velocity in excess of the velocity of movement of said elec- -trodes to cause successive illumination of unitsections of the area tofbe scanned, 9.: Scanning apparatus forv television an the like, comprising a pairof relatively movable linear electrodesystems, means for maintaining between said electrodes 2. potential suflicient to cause a discharge, and means for moving said electrodes through overlapping I :relation at a slight angle,whereby-said discharge is caused to travel along said elec-' trodes withia-velocity in excess of the ve-;

alocity of movement of said electrodes. to cause successive illumination of -un1t sectlons of theareatobescanned. V i a 10. Scanning apparatus fortelevision and .the like,comprising a pair of-relatively'mov o l able linear electrode systems, means formaintaining between said electrode systems a po tential 's'uflicient to cause a discharge ,and means for moving said electrodes in a direc-' tion difi'erent from that of the desired dis.- charge movement to cause successive illumination ofunit sections of the area to be scanned.

-11. In a scanning system vfor a television system, twosets of relatively movable mediums, means for maintainingbetween two of i said mediums of each set a constant distance of separation and a potential difference sufficient to form an arc therebet ween, and means for moving said-sets of mediums relatively'to one another, said mediums producing between any two thereof a unit light ray to'traverse an object with a velocity in excess of the velocity of movement of said mediums to causesuccessive illumination of unit sections of the area to be scanned. v

i 12., In a scanning system for television and the like, a'pair of relatively movable mediums atleast one of said mediums" including a plurality of members, means for maintain- I ing one of said mediums at a constant distance of separation from 1 any one of said members, meansfor producmgan electrical discharge between one of said mediums and any one OfSflld members,,-and means for moving one of said mediums and any one of said members relatively to one another in'such a manner as to cause said light area to travel along said mediums with a velocity inexcess of the velocity of movement of said mediums to provide successive illumination of unit sections of the area to be scanned at a rate to present the illusion of motion".

13. In a scanning system for television and the like, a pai'rof movable electrodes, means for maintaining between said electrodes a potential diiference suffic'ient tocause a discharge, and means for moving said electrodes in such a manner as to cause said discharge in, eifect'to travel between said electrodes with a velocity inexcess of the velocityof movementof said electrodes to cause successive illumination of unit sections of the. area to be, scanned at arateto present theillusion iofvmotion. f 1,; 14.=-In a scanning system for television and the like, a pair of movable electrodes,

"means for .maintaining between said elec- :trodes a potential difference suflicient to cause'a discharge, and means for moving said electrodes through overlapping relation at a slight angle, whereby. said discharge is caused in effect to travelijbetween said electrodes;

with a velocity in excess of the velocity of movement of saidelectrodes to cause successive illumination of unit sections of the area to' bescanned-at .a rate to present the illusion of motion.

15. Scanning apparatus for television and i the like, comprising a pair of movable electrodes, means for maintaining-between said electrodes apotential difference suflicient to cause a discharge therebetween, and means formoving said electrodes in a directiondif- ;ferent from that of the desired discharge movement to cause successlve illummation of un1t sections of the'area to be scanned.

16. The method of scanning for television andithelike which comprises maintaining between a pair of movable electrodes a difference of potential suflicient to-cause a' discharge to pass between them, and moving said electrodes in such a manner as to cause said discharge in effect to travel between said electrodes 'with a velocity in excess of the velocityof movement of said-electrodes to cause successive illumination of unit sections of the area to be scanned.

17. The method of scanning for television and the like, which comprises maintaining between a pair of movable electrodes a difference of potential suflicient to cause a discharge to pass between them, and varying the position of the electrodes to cause said discharge to move'with a velocity in excess of the velocity of movement of said electrodes, and in a'direction other than the direction of such movement to cause successive illumination of unit sections of the area'to be'scanned. 1

18. The method of scanning for television and the like which comprises .maintaining between a pair of mediums a constant distance of separation, saidmediums producing a unit light area therebetween, and moving said electrodes relatively to one another in such manner as to causesaid light area to travel'along said mediums with a velocity in excess of the velocity of movement of said mediums to provide successive illumination of unit sections of the area to be scanned.

, Witness'my handthis 11th day of Decem- 'ber, 1930, at the cityof Newark, in the county of Essex, and-State of New Jersey. ALEXANDER MoLEAN NIGOLSON. 

